Thyroid storm! Or is it?… 8/28/18

Thanks Hong for presenting the case of a middle-aged woman with recent diagnosis of Grave’s disease off methimazole who presented with A fib with RVR and congestive heart failure, raising a debate on thyroid storm!


Clinical Pearls:

  • Thyroid storm is an extremely rare (1 in 500,000) but life-threatening diagnosis (up to 30% mortality) that should not be missed.
  • Degree of thyroid hormone elevation or TSH suppression is not a criteria for diagnosing thyroid storm! In fact, levels are typically similar to those of patients with uncomplicated thyrotoxicosis.
  • Common clinical feature is cardiovascular symptoms (heart failure, arrhythmia, tachycardia) but more specific finding is AMS.
  • Scoring criteria to screen for thyroid storm include Burch/Wartofsky and the Akamizu criteria, but they have not been validated.
  • Consult endocrine early if you suspect thyroid storm!

Thyroid storm: 

Risk factors:

  • Longstanding untreated hyperthyroidism
  • Precipitants:
    • Thyroid/non-thyroidal surgery
    • Trauma
    • Infection
    • Acute iodine load
    • Parturition
    • Irregular use or discontinuation of antithyroid treatment

Etiology: not clearly understood, but possibly related to the following

  • Rapid rate of increase in thyroid hormone levels?
  • Increased responsiveness to catecholamines?
  • Enhanced cellular responses to thyroid hormone?
  • The degree of thyroid hormone elevation or TSH suppression is not typically more profound than uncomplicated thyrotoxicosis

Clinical features:

  • CV (>60% of cases)
    • Tachycardia
    • CHF
    • Arrhythmias
  • Hyperpyrexia
  • AMS (considered by many to be essential to diagnosis)
    • Agitation, anxiety, delirium, psychosis, stupor, coma
  • Features associated with worse outcomes?
    • AMS
    • Older age >60
    • Mechanical ventilation
    • Not using antithyroid drugs or beta blockers

Diagnosis: 

  • Clinical! No universally accepted criteria or validated clinical tools.  Degree of hyperthyroidism is not a criterion for diagnosis.  Some to know of that might be helpful:
    • Burch and Wartofsky (sensitive, not specific)
      • > 45: highly suggestive of thyroid storm
      • 25 – 44: impending storm
      • <25: thyroid storm unlikely
    • Akamizu (Japanese) system developed in 2012 (less sensitive but more specific)

Treatment

  • ICU admission!
  • Regimen
    • Beta blockers ⇒ control symptoms from increased adrenergic tone
    • Thionamide ⇒ block new hormone synthesis. PTU is preferred because it blocks peripheral conversion of T4 to T3.
    • Iodine solution ⇒ block release of thyroid hormone (saturated solution of potassium iodide)
    • Iodinated radiocontrast agent (not available anymore in most places) ⇒  inhibit peripheral conversion of T4 to T3
    • Glucocorticoids ⇒ reduce T4 to T3 conversion, promote vasomotor stability, and treat any associated relative adrenal insufficiency
    • Bile acid sequestrants ⇒ decrease enterohepatic recycling of thyroid hormones (only in very severe cases)
  • Principles
    • Start with beta blockers + PTU, and stress dose steroids
    • 1 hour later: start SSKI q6h (after hormone synthesis has been halted with PTU, otherwise SSKI can make thyroid storm worse)

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